Resolved after 17 hours 47 minutes, affecting Mail Flow and Mail Flow, on January 21, 2026.
On Wednesday, January 21, 2026, from approximately 14:59 to Thursday, January 22, 2026, at approximately 10:11 \(UTC\), some customers experienced delays with outbound email delivery for UK instances of Prevent, Defend, and Protect. This incident was caused by an external email reputation service provider that temporarily restricted one of our outbound email IP addresses. Some messages routed through this restricted address experienced temporary delays while we attempted delivery using other sending addresses. To resolve this issue, our team reached out to the service provider to have the IP address taken off their blocklist. Once the restriction was lifted at 17:33 \(UTC\), our systems automatically retried the remaining queued messages, and outbound email delivery returned to normal performance by January 22, 2026, at 10:11 \(UTC\). To prevent this type of issue in the future, we are investigating additional mitigations for external reputation factors. We are also enhancing our existing monitoring to identify and respond to outbound email reputation changes more quickly. No data loss occurred as a result of this issue.
Affected components
Update timeline
- monitoring Jan 21, 2026, 06:18 PM UTC
We've received reports of some customers having mail flow issues intermittently. We have identified and implemented a fix, however the fix may take 1-4 hours to propagate.
- resolved Jan 22, 2026, 12:05 PM UTC
This incident has been resolved.
- postmortem Feb 04, 2026, 08:49 PM UTC
On Wednesday, January 21, 2026, from approximately 14:59 to Thursday, January 22, 2026, at approximately 10:11 \(UTC\), some customers experienced delays with outbound email delivery for UK instances of Prevent, Defend, and Protect. This incident was caused by an external email reputation service provider that temporarily restricted one of our outbound email IP addresses. Some messages routed through this restricted address experienced temporary delays while we attempted delivery using other sending addresses. To resolve this issue, our team reached out to the service provider to have the IP address taken off their blocklist. Once the restriction was lifted at 17:33 \(UTC\), our systems automatically retried the remaining queued messages, and outbound email delivery returned to normal performance by January 22, 2026, at 10:11 \(UTC\). To prevent this type of issue in the future, we are investigating additional mitigations for external reputation factors. We are also enhancing our existing monitoring to identify and respond to outbound email reputation changes more quickly. No data loss occurred as a result of this issue.
Your product runs on more than KnowBe4
Add the vendors you depend on and get one message when any of them reports trouble. Free for 3 vendors, no card.
Amazon Web Services